Cycloolefins are materials useful in the production of other high value products. For instance, in the commercial production of the polyamide known as NYLON 66, cyclohexene is first converted to cyclohexanol. The cyclohexanol is then oxidized to adipic acid with nitric acid, converted to a salt, and finally converted to the polymer. Other members of the cycloolefin family have similar utility.
The previously used hydrogenation processes have fallen into two classes: one class consists of multistep processes starting with benzene or substituted benzenes and produces cyclohexanes or halocyclohexanes as intermediates. For instance, one such process involved the steps of hydrogenating benzene to form cyclohexane, oxidizing the cyclohexane to produce cyclohexanol, and dehydrating the cyclohexanol to produce cyclohexene. The other major multistep process involves the steps of halogenating benzene to produce a halobenzene, hydrogenating the resulting product to halocyclohexane, and dehydrohalogenating the halocyclohexane to cyclohexene.
The other class of processes is a single step synthesis in which monocyclic aromatics are only partially hydrogenated to form the corresponding cycloolefins. Ruthenium catalysts are often used in these processes.
U.S. Pat. No. 3,912,787 discloses a partial hydrogenation process for the production of cyclic olefins using an aqueous dispersion of a solid ruthenium containing catalyst promoted with a transition metal. The aqueous dispersion is maintained at an essentially neutral or acid pH condition. The catalyst may be supported on well known oxidic supports.
U.S. Pat. No. 4,079,097 to Antos shows a process for dehydrogenating hydrocarbons using composite catalysts of a combination of a platinum group component, a cobalt component, and a bismuth component all on a porous catalytic carrier.
U.S. Pat. No. 4,197,415 shows a process for selectively partially hydrogenating aromatic hydrocarbons to cyclic olefins by contacting the aromatic hydrocarbon with hydrogen and a ruthenium catalyst in an aqueous dispersion containing the salt of a phosphorous acid. The ruthenium catalyst may also be promoted by one of a large number of metals preferably, however, indium, copper, or silver.
U.S. Pat. No. 4,392,001 to Don et al. shows a process for the partial hydrogenation of an aromatic hydrocarbon in the gas phase using a ruthenium catalyst. The reaction takes place in the presence of water vapor.
U.S. Pat. No. 4,495,373 to Niwa et al. shows an improved catalyst system for the partial hydrogenation of an aromatic hydrocarbon compound in the liquid phase using an admixture of water and a ruthenium-containing solid catalyst. The catalyst is prepared by the hydrolysis gelation of a silicon or aluminum alkoxide in a solution containing a ruthenium compound such as ruthenium alkoxide. After gelation, the gelled material is dried. Copper may be included in the gel catalyst. The patent suggests that the resulting catalyst provides "improved catalyst activity and selectivity" in a partial hydrogenation of an aromatic compound over conventional ruthenium-containing catalysts prepared by later impregnation of a preformed silica gel carrier.
U.S. Pat. No. 4,575,572 to Ichihashi et al. also shows a process for partially hydrogenating aromatic hydrocarbons using a catalyst of ruthenium and at least one of iron, cobalt, silver, and copper supported on a barium sulfate carrier all in the presence of water.
U.S. Pat. No. 4,665,274 to Ichihashi et al. discloses a process for producing cycloolefins by partial hydrogenation of the corresponding aromatic hydrocarbon with hydrogen gas in the presence of water and a catalyst of ruthenium and one or more metals selected from iron, cobalt, silver, and copper supported on a barium sulfate carrier. The carrier also includes one or more of silica, titania, and alumina.
U.S. Pat. No. 4,678,861 to Mitsui et al (assigned to Asahi Kasei Kogyo K. K.) teaches a process for producing cycloolefins by partially hydrogenating a monocyclic aromatic hydrocarbon in the presence of a supported ruthenium catalyst comprising a rare earth element (apparently preferably lanthanum). The ruthenium may be present in an amount between 0.1 and 10% of the overall weight of the catalyst. The process is carried out in a multiphase reaction medium of water, hydrocarbon, catalyst, and hydrogen. The aqueous phase preferably is alkaline and contains dissolved ZnO or Zn(OH).sub.2.
U.S. Pat. No. 4,734,536 to Nagahara et al. shows a process for producing a cycloolefin by a partial hydrogenation of a monocylic aromatic hydrocarbon using a neutral or acidic aqueous solution in the presence of a particulate hydrogenation catalyst of metallic ruthenium having an average crystallite size of 200 .ANG. or less, zinc compound as a promoter, and at least one additive selected from the group of oxides, hydroxides, and hydrates of Zr, Hf, Ti, Nb, Ta, Cr, Fe, Co, Al, Ga, and Si.
Japanese Kokai 61-085,334 discloses the preparation of cycloolefin by partial hydrogenation of aromatic hydrocarbons using a ruthenium-silica catalyst which has been activated through the use of an aliphatic polyhydric alcohol.
Japanese Kokai 62-045544 (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, finely crystalline metallic ruthenium (desirably below 200 .ANG., most preferably below 100 .ANG.) containing zinc, and an acid (preferably sulfuric acid) to form a solution having a pH between 2.0 and 6.5.
Japanese Kokai 62-067033 to Nagahara et al (assigned to the Asahi Chemical Industry Co.) teaches that the deactivation of Ru-impregnated La(OH).sub.3 catalysts in benzene partial hydrogenation reactions may be minimized by preventing the accumulation of Fe on the catalyst.
Japanese Kokai 62-081331 to Nagahara et al (assigned to the Asahi Chemical Industry co.) teaches that the deactivation of Ru-metal catalysts in benzene partial hydrogenation reactions using water as the reaction medium may be minimized by using reactors having walls of titanium or zirconium.
Japanese Kokai 62-081332 to Nagahara et al. (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, finely crystalline metallic ruthenium, and ZrO.sub.2 or HfO.sub.2.
Japanese Kokai 62-108826 (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, finely crystalline metallic ruthenium (desirably below 200 .ANG., most preferably below 100 .ANG.), salts of Group IA or IIA metals (preferably zinc sulphate) and an acid (preferably sulfuric acid) to form a solution having a pH between 0.5 and 7.0.
Japanese Kokai 62-142126 to Ichihashi et al. (assigned to the Sumitomo Chemical Co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, ruthenium on supports of Group IA alkali metal salts of phosphorous oxoacids, and salts of phosphorous oxoacids as additives (optionally, with a metal of iron, cobalt, nickel, copper, silver, or zinc--particularly zinc, aluminum, barium, and cobalt orthophosphate). An example showed 3.8% conversion of benzene and 50.8% selectivity to cyclohexene.
Japanese Kokai 62-205037 to Nagahara et al (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, finely crystalline metallic ruthenium (desirably below 200 .ANG., most preferably below 100 .ANG.), and solid basic zinc sulphate.
Japanese Kokai 62-255438 to Niwa et al (assigned to Fuji K. K. and the Agency of Industrial Science and Technology) suggests a process for partially hydrogenating an aromatic hydrocarbon in the presence of H.sub.2 with a catalyst of ruthenium and copper prepared by dispersing those metals in a solid obtained from a metal hydroxide (preferably silica, alumina, or zirconia) colloid.
Japanese Kokai 62-294,422 assigned to Asahi Chemical Industries, K. K., shows a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water, a hydrogenating catalyst containing fine crystallite ruthenium, and a solid basic zinc sulfate. The conversion of benzene is said to be about 70% and the selectivity to cyclohexene is said to be 70% to 80%.
Japanese Kokai 63-048232 (assigned to the Asahi Chemical Industry Co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of a ruthenium catalyst on a carrier, zinc oxide or hydroxide, and water containing an accelerator selected from salts of Group IA or IIA metals, manganese, zinc or cobalt.
Japanese Kokai 63-88139 to Nagahara et al. (assigned to the Asahi Chemical Industries Co.) shows a process for partially hydrogenating single ring aromatics using hydrogen in the presence of a neutral to acidic aqueous solution and a hydrogenation catalyst containing metallic ruthenium crystallites with a diameter of 200 .ANG. or less, at least one separate metal hydroxide or hydrated metal oxide selected from Ti, Zr, Hf, Nb, Ta, Cr, Fe, Co, Al, Ga, and Si, and further containing at least one solid basic zinc salt.
Japanese Kokai 63-152333 (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of solid basic zinc compounds in neutral or acidic water and metallic ruthenium on a support (preferably gamma-alumina).
Japanese Kokai 63-243038 (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of zinc compounds in neutral or acidic water and finely crystalline metallic ruthenium (desirably between 30 .ANG. and 200 .ANG., most preferably between 40 .ANG. and 100 .ANG.) on a support (preferably ZrO.sub.2 or HfO.sub.2).
Japanese Kokai 63-243039 (assigned to the Asahi Chemical Industry co.) teaches a process for the partial hydrogenation of monocyclic aromatic hydrocarbons in the presence of water; a hydrogenation catalyst of colloidal metallic ruthenium on a metal salt, hydroxide, or oxide support; and a soluble zinc compound.
Japanese Kokai 1-159,059 to Nagahara et al. shows a process for regenerating a ruthenium catalyst which has been used for partial hydrogenation of a cycloaromatic. The catalyst is regenerated by contacting the catalyst with oxygen or with sodium chlorite.
A Japanese publication entitled Senryotoyakuhin, 1986, 31 (11), 297-308 (Japan) discloses a process for preparing cyclohexene by partial hydrogenation of benzene. The reaction takes place in an aqueous medium at about 150.degree. C. to 200.degree. C. and 30 atmospheres to 70 atmospheres in the presence of a ruthenium catalyst and a copper, silver, or cobalt promoter.
Niwa et al. in a letter in the Journal of Molecular Catalysis (34, 1986) 247-249, entitled "Selective Hydrogenation of Benzene to Cyclohexene with New Ruthenium Catalyst Prepared by Chemical Mixing Procedure" discloses a process for partial hydrogenation of benzene using desirably a catalyst of ruthenium and copper on silica. The communication shows a cyclohexene yield of 31% and a benzene conversion of 83%.
Niwa et al. in J. Chem. Tech. Biotechnol. 1986, 36, 236-246, shows the partial hydrogenation of benzene with a ruthenium catalyst prepared by a specific chemical mixing procedure. The catalysts are made by mixing ruthenium chloride and (optionally, copper chloride) with a diol such as ethylene glycol to form a solution of metal complexes. Tetraethoxysilane was added to the prior solution and water was added to hydrolyze the various metal alkoxides formed during the stirring. The material was then gelled and dried to form the catalyst.
Published European Patent Application 0,323,192 shows a hydrogenation catalyst prepared by adsorbing ruthenium ions on a hydrotalcite clay and then reducing the adsorbed ruthenium ions. The catalyst is said to be suitable for use in partly reducing monocyclic aromatic hydrocarbons to cyclohexene.
None of the cited references suggest a process for producing cyclic olefins using a ruthenium-based catalyst on a composite support into which a selectivity promoter has been incorporated, nor do the references suggest that such process operates in the absence of soluble selectivity promoter additives in the aqueous phase. The catalyst and process of the present invention have several advantages over the prior art. The inventive process shows very high yields with very efficient catalysts. The prior art does not suggest that a supported catalyst is capable of such high yields in any similar process. The prior art does not suggest the existence of any unsupported or precipitated catalyst having such high efficiencies or productivities (when measured on a ruthenium basis). The process of the present invention can be operated at neutral pH and in the absence of added salts and is, therefore, more compatible with lower cost materials of construction than, for example, processes cited in the prior art utilizing sulfuric acid or large amounts of dissolved salts in the aqueous phase.